If you apply a fertilizer on acidic soil, a big percentage of the nutrients will not be absorbed by the plants, hence wasted. Take, for instance, complete fertilizer which contains 14% nitrogen (N), 14% phosphorus (P), and 14% potassium (K). If you apply this on a soil with 4.5 pH which is Extremely Acidic, only 30% N, 23% P and 33% K are absorbed, hence 71.34% is wasted.
When the soil has 5.0 pH, considered Very Acidic, only 53% N, 34% P and 52% K are taken up by the plants. This means 53.67% is wasted.
With a 5.5 pH, considered Acidic, 77% N, 48% P and 77% K are absorbed. That means a loss of 32.69%. If the pH is 6.0, Slightly Acidic, 89% N, 52% P and 100% K are absorbed. There’s a loss of only 19.67%.
Now, if the pH is 7.0, Neutral, 100% of the NPK is absorbed by the plants. There is 0 wastage.
How do you decrease the acidity of soils? This is done by applying agricultural lime. You can check with a pH meter if you have attained the desired acidity or alkalinity of your soil.
A Neutral pH (7,0) is not necessarily the ideal pH for all plants. The Department of Soil Science of UP Los Baños had published a booklet, Soil Analysis and Fertilizer Usage, which reports the ideal pH for various crops.
(Editor’s Note: This is the second of a series of simple but very useful information from the booklet published by Zetryl Chem. Watch for the next postings. We will feature more about the different types of fertilizers for different crops.